Using electron waveshaping with graphene to produce strong, targeted X-rays
(News from Nanowerk) A new energy-efficient method for producing highly focused and finely controlled X-rays that are up to a thousand times more intense than those from traditional methods has been developed and simulated by scientists led by Nanyang Technological University, Singapore (NTU Singapore) (Light: Science & Applications, “Free-electron crystals for enhanced X-ray radiation”).This opens the door to super high-quality X-ray imaging, which use potent X-rays to precisely detect defects in semi-conductor devices. The new technique may also enable less energy-intensive, more targeted X-ray imaging for health screening.
The innovative technique fires electrons at ultra-thin materials with highly organised structures, like graphene, using computer simulations. The fundamental working principle is the same as that of the traditional X-ray tube production method. There’s a catch, though: the simulations’ wave-like patterns of electron flight are “shaped” in a very particular way, matching and overlapping the highly structured positions of the material’s atoms on the particle’s route.
In theory, this leads to the emission of X-rays at significantly higher intensities than usual. These can be precisely regulated to produce X-rays in multiple directions or in one broad direction.
Bremsstrahlung, often known as “braking radiation,” is the process by which fired electrons are typically deflected and release X-rays when they clash with material atoms.
When generating radiation with X-ray tubes, the majority of the radiation is released due to bremsstrahlung. However, since the X-rays are released in various directions, one issue is that they are not concentrated. By filtering the X-rays so that only those released in the desired direction are used, current approaches attempt to overcome this. Even yet, the X-rays remain rather dispersed while being filtered.
By altering the path taken by the discharged electrons in computer simulations, a group of scientists from across the world, lead by Nanyang Assistant Professor Wong Liang Jie from NTU’s School of Electrical and Electronic Engineering, were able to solve these difficulties.
The other researchers are affiliated with the University of California, Los Angeles, Technion – Israel Institute of Technology, Stanford University, Tel Aviv University, and Singapore University of Technology and Design.
The researchers used computers to simulate electrons moving through a specially designed plate that is also conducting current in order to produce a voltage. Through simulations, the scientists were able to demonstrate how electron waveshaping—an phenomena that occurs when an electron passes through a “phase plate” of this kind—affects the way the electrons travel.
This occurs because, according to quantum physics, electron particles are able to move in a wave pattern similar to that of light waves. Because of this, previous studies have demonstrated that after going through a phase plate, they can interfere with one another.
The pattern of the electrons’ wave-like movement is also affected by changes in the plate’s voltage, and these changes can also be made to the wave pattern of the electrons.
Subsequently, the simulated electrons were directed towards an extremely thin graphene material, which is around 1,000 times thinner than a human hair strand.
The course of flight of these electrons has a strong inclination to align with the hexagonal orientations of the atoms in graphene because of their particular form.
This raised the likelihood that the electrons would crash into the atoms, and the simulations indicated that this would cause additional X-rays to be released, intensifying the radiation that was created.
The new approach was also more energy-efficient, according to the simulations. The X-rays produced by the researchers’ method were up to a thousand times more intense than those produced by conventional methods employing X-ray tubes, all while using the same amount of current to fire electrons. Modifications to the phase plate could potentially be used to alter the radiation’s intensity.
The new technology allows future X-ray generating gadgets to be more tuneable than previously because it can focus the X-rays in one broad direction or emit them in multiple directions depending on what they are utilised for. Through simulations, this fine control was attained by varying the plate voltage, which altered the electrons’ travel path and pattern.
The X-rays generated were more dispersed when the wave pattern of the electrons tended to overlap with the surface of whole atoms. X-rays were produced in one general direction by adjusting the plate’s voltage so that the electrons’ wave pattern coincided with the ring-shaped layers surrounding the atoms.
The focused X-rays were probably created as a result of altered electron-atom interactions, which caused X-ray interference that eliminated some X-rays emitted in one direction while reinforcing others in another.
The new technique could lead to the development of smaller X-ray generating devices since it uses less energy to create intense X-rays. Standard machines might therefore be reduced in size from potentially larger than a house to something that could fit on a table.
Although commercial equipment capable of electron waveshaping already exist, it is a novel application to generate tuneable, high-intensity X-rays, as previous studies have attempted to manipulate other forms of radiation through electron waveshaping.
The scientists under the direction of Asst Prof Wong were motivated by these earlier attempts to experiment with waveshaping X-rays in computer models in order to observe how results varied with different parameter adjustments. Based on one of these simulated tests, which revealed that altering the electron’s path could boost the X-rays’ brightness, the most recent study was conducted.
The strong X-rays generated by the scientists’ technique might be used to create extremely high-resolution X-ray photographs of semiconductor chips in order to more precisely identify any difficult-to-see defects in manufactured chips.
The novel technology could provide more flexibility in providing X-ray imaging for health screening, such as imaging a full hand or just a finger joint, while using less energy to produce the radiation, since the X-rays produced could be adjusted to be either diffused or focused.
Intense and focused X-rays may potentially be useful for more precisely targeted radiation in the treatment of cancer.
Presently, the scientists intend to conduct studies to validate the outcomes of their simulations.
Asst Prof. Wong stated: “The generated X-rays are dependent on the accuracy of electron waveshaping.” We think our suggested method can be completely realised for intense and highly tuneable table-top X-ray technology given the quick development of electron-waveshaping techniques.